Deformable intraocular lenses are used both for replacement of the natural lens in cataract afflicted eyes and for surgical implantation of an additional lens for refraction correction purposes. In a typical cataract operation the eye ball is punctured close to the limbus and an instrument is inserted and used to disintegrate and remove the opaque eye lens. Next an artificial lens is inserted through the incision to replace the natural lens and is kept in place, normally in the posterior chamber, by haptics in the form of either flexible wings (one piece lens) or flexible spiraling legs (two or more piece lenses) later developed for better stabilization in the eye. Healon (R) or a similar agent is introduced during both steps in order both provide bulk and protect sensitive tissue during the operation. The procedure is about the same for phakic corrective lenses although the natural lens is normally not removed and the thinner lenses can be located also in the anterior chamber in front of the iris.
The eye incision size necessary is determined by the lens size and the first generation of hard lenses, typically made from PMMA, required a cut corresponding to the lens diameter. Soft lenses have been developed for the purpose of limiting the incision needed to insert the lens in the eye, thereby reducing the risks for eye ball distortions and infections and improving post-operative healing. The soft lens, e.g. made from silicone, can be folded or rolled to a fraction of its initial diameter and then regains its original shape within the eye. Yet, manual folding followed by insertion, release and manipulation of the lens through the minimal incision requires the physician to execute high skill and various tools have been developed and marketed to facilitate these steps. Typical general problems include the establishment and maintenance, without tearing, of the small incision not to introduce deformation and subsequent astigmatism, not to touch the cornea or the thin endothelial cell layer, to control the positioning of both lens optic part and especially the flying haptics and to avoid any infection or introduction of debris into the eye.
Although the deformable lenses have solved a lot of problems, other are introduced instead. The lens material is softer and more susceptible to damage, cutting or shear by hard or sharp parts or imperfections in implanters or other manipulating devices, problems exaggerated by the material friction making the material easily caught in tolerances necessarily present between device parts. Also the lens haptic parts need consideration. The lens has to be folded or deformed so as to avoid collision or overlap between the haptics and their anchoring points in particular, yet not so far separated that a plunger attacks directly thereon. It has to be folded not to be damaged during transport and to be released and unfolded properly at exit. Most lenses are asymmetrical with a distal and a proximal side and need to be ejected in proper oriented in the eye. Yet the very necessity that the haptics are the most peripheral lens parts makes them especially exposed and, furthermore, force applied thereto give high torque and twisting moment to the lens, easily resulting in misalignment or rotation of the whole lens, in turn resulting in improper folding or deformation, damage to haptics or optics and improper release at exit, all most often manifested in abnormally high displacement resistance.
These soft lens characteristics put severe-demands on any device for their manipulation and implanters with lens transportation channels in particular. The overall demand on such a channel is that it should be smooth not to impose shear, friction, grinding, cutting or pinch to the lens optic or haptic and this applies both to any transition in monolithic channel parts and to joints in multiple part channels, the latter to be avoided as far as possible as grades and misalignments are almost inevitable unless instead the parts are fused, polished and finally cleaned to avoid any trace of debris. Yet multiple parts may be unavoidable, e.g. when providing for doors or closures to allow lens insertion or when using cartridge type inserts for lenses deformed by separate or external means. In general the lens transport through the channel comprises at least two distinct phases. In a first phase the lens is transported, possibly under complete or partial deformation, to a stand-by position, ready for release, close to the end of an elongated tip designed for insertion through the incision into the eye, although this phase is commonly performed before the tip has been inserted into the eye. In a second phase, performed with the tip inserted into the eye, the lens is pushed the remaining short distance out from the stand-by position for released in the eye. A plunger arrangement need to cope with the different requirements in these phases, the first in general needing a slow but steady force and speed not to stress the lens whereas the second is more of a short triggering action as the lens tend to unfold automatically at the end tip due to its stored elastic energy. The force variations are considerably more pronounced in the first phase if a lens deformation takes place, increasing until completion of deformation and then dropping, and in the second phase if the tip is designed with deformation features or release features, e.g. slits. In manual operation force drops may easily result in inadvertent displacements, especially disastrous at final release. Lens deforming convergent channels poses additional problems, e.g. in respect of controlled initiation as well as continued folding, especially in view of the haptic problems outlined. The problems tend to be more pronounced for the two or more piece lenses with their delicate and elusive spiralling haptics compared to the more sturdy and localized single piece haptics.
Although many tool types have been proposed it is believed that no suggestion meets the abovesaid requirements to any acceptable extent. Early device suggestions were merely auxiliary fixtures or jigs for assisting forceps or hook handling of the lenses, as exemplified by U.S. Pat. No. 4,702,244, U.S. Pat. No. 5,100,410 and U.S. Pat. No. 5,176,686 but neither high deformation degrees nor small incisions could be obtained or acceptable manipulation control. Many later proposals rely on separate means for lens deformation and lens transportation respectively, e.g. jaws, paddles, e.g. U.S. Pat. No. 4,880,000, or deformation members acting lateral to the channel. Such devices necessarily comprises several parts between which the lens is deformed, and the lens deformed between such parts is often inserted as a cartridge into a reusable implanter device, all parts tending to introduce the potentially harmful imperfections described. Moreover, such devices rely on operator skill, rather than assistance by convenient device safety features, for correct lens insertion and manual deformation, easily resulting in arbitrary and inconsistent folding and release behavior. As a typical example the U.S. Pat. Nos. 5,494,484 and 5,800,442 relate to a device for lens deformation between two hinged half tube, wherein skill is required not to invoke random results or pinching of optic or haptic. Although the already deformed lens should allow for a simple plunger advancement mechanism a screw arrangement is used, requiring an impractical two hand operation in the critical moment of lens release. Numerous proposals have also been made for devices with convergent channels in which the lens is folded and deformed during forward transport in the channel before final release at the end. The lens may be inserted flat or slightly bent at the channel entrance for further downstream deformation, proper folding frequently assisted by grooves or other structures in the convergent channel parts. Typical examples are disclosed in U.S. Pat. No. 4,919,130, U.S. Pat. No. 5,275,604, U.S. Pat. No. 5,474,562, U.S. Pat. No. 5,499,987, U.S. Pat. No. 5,584,304, U.S. Pat. No. 5,728,102, U.S. Pat. No. 5,873,879 (WO96/03924), DE 3610925, WO 96/20662 and WO 96/25101. Although such deformation devices may require less operator skill the results are far from satisfactory and consistent. As said, the transport deformation principle requires high and varying transportation forces, increasing stress and possible damage of the lens from channel and plunger. A further cause of lens damage is the fact that such devices have a larger entrance than exit channel cross-section, the added area sometimes added to facilitate insertion of the unstressed lens but always needed to accommodate the plunger cross-section area in the height direction. Shear between channel and plunger is then unavoidable where the cross-section decreases or changes, often causing squeezing or even cutting of the soft lens material in addition to the potentially destructive point force applied between the plunger and the non-deformed lens. Also the initially unfolded lens is highly susceptible to misalignment due to the twisting forces described, often resulting in improper folding and later unfolding or damage to the displaced optic or haptic, in spite of extensive means proposed to accommodate and protect the haptic during lens pushing. Also the problem of convenient use of the device in view of the strongly varying force requirements remains unsolved as well as the risk for actual implantation of a damaged lens due to the masking effect of uncontrolled force variations.
As indicated special problems are experienced with the two or more piece lenses having spiraling haptics with extended flexible legs where with one end attached to the lens optic part and the other end free. Many of these problems are associated with the mobility of such haptics and the difficulties involved in the giving the haptics a proper initial orientation. Typically the haptics have a curvature in un-stressed condition extending a bit out from and around the edge or periphery of the lens optic part to remain outside the optically active area also after some radial fixation compression when inserted in the eye. The peripheral location makes the haptic exposed and its curvature inconsistent with the highly compressed state of the deformable lens prior to release in the eye. Normally the haptics have to be carefully oriented, e.g. both forward or one forward and one rearward with respect to an implanter duct, and also stretched to a less curvature to fit within the duct boundaries. Often the haptics are manually oriented with assistance of only simple tools, such as forceps, even when placed in implanters otherwise highly sophisticated in respect of lens folding and handling features. Manual manipulation means risk for faulty or irreproducible results, especially as different implanters and even lens types or diopters may require different approaches. Accordingly there remains a need for methods and means assisting haptic manipulation.